arXiv subjects

Poulomi Chakraborty

Publications and source records attributed to Poulomi Chakraborty.

4 recordsLinked to original sources

arXiv2026

General Conditions for Axis Dependent Conduction Polarity

Axis-Dependent Conduction Polarity (ADCP) refers to the phenomenon in which electrical transport within a single material is p-type along one crystallographic direction and n-type along the perpendicular direction. This behavior enables a variety of thermoelectric applications that do not require a heterojunction between two different materials. In this work, we investigate ADCP theoretically and derive a set of generic and quantitative criteria for identifying and predicting materials that exhibit ADCP. Specifically, by analyzing the thermopower for generic metals, semimetals, and semiconductors, we obtain transparent inequalities that are both necessary and sufficient for the emergence of ADCP. Moreover, we review known ADCP materials and verify that their band-structure characteristics and relaxation parameters are consistent with the inequalities derived here.

cond-mat.mtrl-sci↗

arXiv2025

Design Principles for Topological Thermoelectrics

Conventional metals, insulators, and semimetals are constrained by fundamental limitations in terms of their thermoelectric performance. Topological materials offer certain features that allow them to circumvent these constraints, and potentially to form the basis for thermoelectric devices with unprecedented efficiency. In this article we review the thermoelectric performance of topological materials, focusing specifically on nodal semimetals, such as Weyl and nodal-line semimetals. We discuss how certain unique ``topological'' features of these materials -- namely their topologically protected band touching points, electron-hole degenerate lowest Landau level, and Berry curvature -- allow them to exhibit thermoelectric properties that go beyond what is possible in conventional materials, particularly in the presence of an applied magnetic field. We focus our discussion on the goal of achieving large figure of merit $zT$, and for each material class we summarize optimal \emph{design principles} for selecting materials that maximize thermoelectric efficiency. We then use these optimal design principles to design and implement a high-throughput database search for topological semimetals that are promising as thermoelectrics. In addition to highlighting a number of materials that are already known to have large magnetothermoelectric effects, our search uncovers twelve additional materials that are especially promising for near-future experiments.

cond-mat.mtrl-sci↗

arXiv2024

Magnetothermopower of nodal line semimetals

The search for materials with large thermopower is of great practical interest. Dirac and Weyl semimetals have recently proven to exhibit superior thermoelectric properties, particularly when subjected to a quantizing magnetic field. Here we consider whether a similar enhancement arises in nodal line semimetals, for which the conduction and valence band meet at a line or ring in momentum space. We compute the Seebeck and Nernst coefficients for arbitrary temperature and magnetic field and we find a wealth of different scaling regimes. Most strikingly, when a sufficiently strong magnetic field is applied along the direction of a straight nodal line or in the plane of a nodal ring, the large degeneracy of states leads to a large, linear-in-$B$ thermopower that is temperature-independent even at low temperatures. Our results suggest that nodal line semimetals may offer significant opportunity for efficient, low-temperature thermoelectrics.

cond-mat.mtrl-sci↗

arXiv2022

Doping as a tuning mechanism for magneto-thermoelectric effects to improve zT in polycrystalline NbP

Weyl semimetals combine topological and semimetallic effects, making them candidates for interesting and effective thermoelectric transport properties. Here, we present experimental results on polycrystalline NbP, demonstrating the simultaneous existence of a large Nernst effect and a large magneto-Seebeck effect, which is typically not observed in a single material at the same temperature. We compare transport results from two polycrystalline samples of NbP with previously published work, observing a shift in the temperature at which the maximum Nernst and magneto-Seebeck thermopowers occur, while still maintaining thermopowers of similar magnitude. Theoretical modeling shows how doping strongly alters both the Seebeck and Nernst magneto-thermopowers by shifting the temperature-dependent chemical potential, and the corresponding calculations provide a consistent interpretation of our results. Thus, we offer doping as a tuning mechanism for shifting magneto-thermoelectric effects to temperatures appropriate for device applications, improving zT at desirable operating temperature. Furthermore, the simultaneous presence of both a large Nernst and magneto-Seebeck thermopower is uncommon and offers unique device advantages if the thermopowers are used additively. Here, we also propose a unique thermoelectric device which would collectively harness the large Nernst and magneto-Seebeck thermopowers to greatly enhance the output and zT of conventional thermoelectric devices.

cond-mat.mtrl-sci↗